In the past a great deal of time has been spent in our laboratory attempting to detect receptor substances for female sex hormones in non-target tissues. Radioactive hormones have been utilized in various assay procedures to label hormone-receptor complexes. It appears that little or no receptor substance is present in the non-target tissues we have surveyed. Yet, female sex hormones produce clinical manifestations in non-target tissues during pregnancy when their levels are very high. Thus, there may be some other mechanism whereby these hormones directly or indirectly influence otherwise non-target tissues. Our next attempts are centering around the concentrations of female sex hormones in various tissues and the blood of laboratory animals utilizing radioimmunoassay techniques. In addition, biopsies of human oral tissue from females in the third trimester of pregnancy and another approximately two months postpartum will be assayed for female sex hormones.